I had uploaded a picture yesterday (...). But unfortunately it is not visible today.

Perhaps it was removed under the rules of the Terms of Service (TOS). Read them carefully before uploading. Moderators/administration may remove the photos that are not according to the TOS. It had happenned to photos of mine.
Don't forget to write a suitable note for your posts.
Perhaps some of your photos are more appropriate to http://www.treknature.com/ or http://www.treklens.com/.